Illustration for a D&D campaign.
Bulrup, the leader of a grung tribe, was badly injured in battle. As a friend and neighbour to the swamp dwelling party of monsters, the oni invented a blood ritual on the spur of the moment to save him. Using his own regenerative blood, the oni successfully healed the grung's wounds. However, there were side effects. A month after healing Bulrup, the grung was stronger, bigger, and had sprouted a couple of oni-like horns. Soon all the grung warriors wanted to be 'Blooded' by the oni.